What Is the Horsepower to Watts Calculator?
This tool converts power expressed in mechanical horsepower (HP) into watts (W), the SI unit of power. It is universal — physics is the same everywhere — and is handy for engineers, students, car enthusiasts, and anyone comparing engine, motor, or appliance power ratings across different unit systems.
How to Use It
Enter the power value in horsepower and the calculator returns the equivalent in watts and kilowatts. The conversion uses the mechanical (imperial) horsepower definition, where 1 HP equals approximately 745.7 watts. Note that metric horsepower (PS) is slightly different at about 735.5 W; this calculator uses the common mechanical HP figure.
The Formula Explained
The relationship is a simple linear conversion: $$P_{\text{W}} = \text{Power (HP)} \times 745.7$$ One mechanical horsepower was historically defined as the power needed to lift 550 foot-pounds per second, which works out to roughly 745.7 watts. To get kilowatts, divide the watt result by 1000.
Worked Example
Suppose a car engine is rated at 150 HP. Multiply: $$150 \times 745.7 = 111{,}855 \text{ watts}$$ or about 111.86 kW. So a 150-horsepower engine produces roughly 111.9 kilowatts of power.
FAQ
Is this mechanical or metric horsepower? It uses mechanical (imperial) horsepower at 745.7 W. Metric horsepower (PS) is about 735.5 W.
How do I convert watts back to horsepower? Divide the watts by 745.7. For example, \(1000 \text{ W} \div 745.7 \approx 1.34\) HP.
What about electrical horsepower? Electrical horsepower is defined as exactly 746 W and is used for electric motors; the difference from 745.7 is tiny.
